Auxiliary drive system
A hydraulic auxiliary drive system for the normally non-driven wheels of a
vehicle to assist the main wheels. The auxiliary drive comprises at least
one variable displacement motor having a swash plate for driving at least
one of the non-driven wheels, a variable displacement pressure compensated
pump supplying the motor with a constant pressure regardless of vehicle
speed, a spring for biasing each motor swash plate toward zero
displacement, a servo connected to the motor swash plate for varying the
displacement of the motor, and a pressure source for supplying the servo.
A manually operated pressure control includes a solenoid-controlled
variable orifice for controlling the pressure level supplied to the servo
to vary the torque output of the normally non-driven wheels. A control
valve is positioned between the pump and motor for disengaging and
reversing the auxiliary drive. Another embodiment includes a second servo
connected to the motor swash plate for decreasing the motor displacement.
A pressure operated valve is located in a sensing passage connecting the
pump outlet with the second servo and has a first position blocking pump
pressure to the servo at all levels above the pressure compensating level
of the pump, and a second position opening pump pressure to the second
servo at a preset pressure level below the compensating level whereby when
the pump reaches full stroke and is unable to maintain its compensating
level, the valve opens causing the motor displacement to decrease.
Beck; Richard A. (West LaFayette, IN), Presley; Glen T. (Angola, IN) |
December 5, 1979|